Self-loading wheel lift devices are commonly used on a number of commercially available tow trucks for lifting a front end (or a rear end if the driver chooses) of a vehicle in order to tow a vehicle. One example of such a self-loading tow truck lift is the Century Express Series by Miller Industries Towing Equipment, Inc. located at 8503 Hilltop Drive, Ooltewah, Tenn. 37363. Such commercially available self-loading trucks can approach an end of the vehicle to be towed at about 90° to the parallel parked vehicle to bring a first end of a cross bar into engagement with the bottom portion of the front tread surface of a first front wheel, and a further backing of the tow truck causes the second end of the cross arm to swing about a pivot such that it brought into engagement with the bottom portion of the front tread surface of the second front wheel. Then, a pair of interior lifts members preferably in the form of L-shaped lift arms are pivoted by a hydraulic actuating mechanism about pivots to close the outer free ends of the lift arm behind the respective wheels in a pincer/like action so that the wheel is captured in a lifting position. This pincer action brings each of the L-shaped lift arms into contact with the bottom portion of the rear wheel tread surface of the first and second front wheels. With the wheels so captured, a boom lift for the cross bar is actuated to lift the cross bar thereby lifting both of the front wheels, and then, the raised front end of the vehicle may be swung outwardly into the street with the vehicle pivoting about the on rear wheels.
Pincer style, self-loading tow trucks can run into difficulties lifting vehicles that have sustained damage to their wheel ball joints, axels or other wheel mount stabilizing structures because the damaged wheel can collapse, tip severely or wobble from its normal vertical orientation such that the upper portion of the wheel collapsing inwardly while the lower portion of the wheel shifts outwardly. This can cause one of three problems; (1) a pronounced wobble in the damaged wheel can cause the pincer action of the lift to fail during an attempt to capture the damaged wheel; (2) where such a wobbly wheel is initially captured, twisting or jarring of the vehicle relative to the lift may cause the damaged wheel to slip free; (3) or, in the most severe cases, the damaged wheel may be collapse so that the frame of the vehicle rests against the ground, which can make it difficult or impossible to get the lift underneath the vehicle in order to capture the wheels. In this third scenario, where one or more wheels have collapsed, it is common for a pincer style, self-loading tow truck operators to call in another style tow truck to move the vehicle, such as, for example, calling for either a hook and chain style truck or a flat bed tow truck. All three of the unstable wheel scenarios discussed above involve significant risks that either the wheel capture process, vehicle lifting, or subsequent towing of a vehicle could result in additional damage to the towed vehicle, the tow truck or its lift mechanism.